Wednesday, February 29, 2012

Teacher ratings

I have been very busy on other things so have only had time to scan the articles over the past week about the release of New York City teacher ratings. One item really jumped out at me, and that was the wide range of the confidence interval for the teacher ratings. As Michael Winerip puts it in his excellent column, posted yesterday (but in today's hard copy paper):

For example, the margin of error is so wide that the average confidence interval around each rating for English spanned 53 percentiles. This means that if a teacher was rated a 40, she might actually be as dangerous as a 13.5 or as inspiring as a 66.5.
Think of it this way: Mayor Michael R. Bloomberg is seeking re-election and gives his pollsters $1 million to figure out how he’s doing. The pollsters come back and say, “Mr. Mayor, somewhere between 13.5 percent and 66.5 percent of the electorate prefer you.”

More to come on this issue, I think. But Winerip's column is a good place to start.

Update, March 4: I always maintain that you can't analyze or understand data without knowing or understanding the context. Here's a very interesting Op-Ed by a teacher, on that provides some much-needed context.